Rom. 12:17-21.
Do not think yourselves wise. Do not repay evil with evil. Make every effort to be respectable to everyone. If it is possible, as much as is in you, be at peace with all men. Do not avenge yourselves, my beloved, but give place to wrath; for it is written: Vengeance is mine; I will repay, saith the Lord. If therefore thine enemy hunger, feed him; if he thirst, give him drink. If thou do this, thou shalt heap coals of fire upon his head. Do not let evil overcome you, but overcome evil with good.
This epistle is laid out in the epistle of the next preceding Sunday, look for it there.